This invention is directed to the method and apparatus for the production of holographic optical elements. Holographic optical elements are finding a variety of uses, including helmet mounted displays such as disclosed in U.S. Pat. No. 3,928,108, and head-up displays such as disclosed in Withrington U.S. Pat. No. 3,940,204. Hologram optical elements are also useful in eye protection reflectors for laser radiation, and for novelty optical effects such as pendant jewelry.
In addition to the above patents the background also includes Withrington et al U.S. Pat. No. 4,218,111 as well as an article "Holographic Optical Elements" published by D. H. Close in the Sept-Oct 1975 issue of "Optical Engineering". All of the background references are incorporated herein in their entirety by this reference.
Such holographic optical elements have been produced by interfering patterns of coherent radiation to produce an image in a photosensitive substrate. Since the patterns are produced by interference of optical waves, the structure must be rigid during exposure because shifting causes destruction of the interference pattern. Since the wavelength is short, very great care must be taken to properly hold all of the elements in place. Thus, there is need for a method and apparatus by which holographic optical elements can be produced without that difficulty.